Rivet analyses

title: BELLE_2013_I1247059

$B^0\to\phi K^*$ decays

Experiment: BELLE (KEKB)

Inspire ID: 1247059

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 88 (2013) 7, 072004

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0, originally Upsilon(4S) decay

Measurment of mass and angular distributions in $B^0\to\phi K^*$ decays. The data were read from the figures in the paper and may not be corrected.

Source code:BELLE_2013_I1247059.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B0 -> phi K* class BELLE_2013_I1247059 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1247059);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
  declare(ufs, "UFS");
  DecayedParticles B0(ufs);
  B0.addStable(333);
  declare(B0, "B0");
  // histograms
  for (unsigned int ix = 0; ix < 4; ++ix) book(_h[ix], 1, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{321, 1}, {-211, 1}, {333, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {211, 1}, {333, 1}};
  DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
  // loop over particles
  for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
    int sign = 1;
    if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particle& Kp = B0.decayProducts()[ix].at(321 * sign)[0];
    const Particle& pim = B0.decayProducts()[ix].at(-211 * sign)[0];
    const Particle& phi = B0.decayProducts()[ix].at(333)[0];
    if (phi.children().size() != 2 || phi.children()[0].pid() != -phi.children()[1].pid()
        || phi.children()[0].abspid() != 321)
      continue;
    Particle Kp1 = phi.children()[0];
    Particle Km1 = phi.children()[1];
    if (Kp1.pid() < 0) swap(Kp1, Km1);
    // B0 frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        B0.decaying()[ix].momentum().betaVec());
    FourMomentum pKstar = boost1.transform(Kp.momentum() + pim.momentum());
    FourMomentum pPhi = boost1.transform(phi.momentum());
    // stuff in K* frame
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
    FourMomentum pKp = boost2.transform(boost1.transform(Kp.momentum()));
    Vector3 axis1 = pKstar.p3().unit();
    double cTheta1 = axis1.dot(pKp.p3().unit());
    if (cTheta1 > 0.75) continue;
    Vector3 trans1 = pKp.p3() - cTheta1 * pKp.p3().mod() * axis1;
    // stuff in phi frame
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
    FourMomentum pKp1 = boost3.transform(boost1.transform(Kp1.momentum()));
    Vector3 axis2 = pPhi.p3().unit();
    double cTheta2 = axis2.dot(pKp1.p3().unit());
    Vector3 trans2 = pKp1.p3() - cTheta2 * pKp1.p3().mod() * axis2;
    // angle between planes
    double chi = atan2(trans1.cross(trans2).dot(axis1), trans1.dot(trans2));
    // fill histos
    _h[0]->fill(pKstar.mass());
    _h[1]->fill(cTheta1);
    _h[2]->fill(cTheta2);
    _h[3]->fill(chi);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 4; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[4];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2013_I1247059);

} ```